Move the nine #undef's common to all qt_*.cpp sources into qt_pre.h. Make "hack.h" usage consistent; always enclose withing 'extern "C {' and '}' even though only some of the sources care.
removes recently added win/Qt/qt_undef.h and win/Qt/qt_redef.h adds win/Qt/qt_pre.h win/Qt/qt_post.h